The considerable activity in the area of organic thin films, involving very thin polymeric films and molecular monolayers and multilayers, led to the formation of a panel, sponsored by the Materials Sciences Division of the Department of Energy, to review this field. Its purpose was to better understand the relevant scientific topics and to suggest suitable areas of research. In particular, a number of potential applications were identified, which require further scientific advances for them to see fruition. These include nonlinear and active optical devices, chemical, biochemical, and physical sensors, protective layers (e.g., for passivation), patternable materials both for resists and for mass information storage, surface modification (e.g., wetting and electrochemical electrode properties), and synthetic biomacromolecules. Studies of these films have the added advantage that they could lead to a better scientific understanding of such subjects as the relationships between the microstructure of ordered molecular arrays and their collective properties, the tailoring of interfaces and surfaces, especially when used to model multibody interactions, and the physical and chemical reactions of films involving phase transitions and intraand interfilm transport. The areas that appear to require the most attention include the application of new characterization techniques, such as the scanning tunneling microscope, the improvement of mechanical and thermal stability, the identification and characterization of physical and chemical defects, and the effects of internal ordering on macroscopic properties. It is further recommended that strong interdisciplinary efforts be mounted to address and solve these problems.

Contact antimicrobial coatings with poly(alkylammonium) compositions have been a subject of increasing interest in part because of the contribution of biocide release coatings to antibiotic resistance. Herein, a concept for antimicrobial coatings is developed on the basis of the thermodynamically driven surface concentration of soft block side chains. The concept incorporates structural and compositional guidance from naturally occurring antimicrobial proteins and achieves compositional economy via a polymer-surface modifier (PSM). To implement this concept, polyurethanes were prepared having random copolymer 1,3-propylene oxide soft blocks with alkylammonium and either trifluoroethoxy or PEGlyted side chains. Six carbon (C6) and twelve carbon (C12) alkylammonium chain lengths were used. The PSMs were first tested as 100% coatings and were highly effective against aerosol challenges of Gram-negative bacteria (Pseudomonas aeruginosa and Escherichia coli). To evaluate the surface concentration, solutions containing 2 wt % PSM with a conventional polyurethane were evaporatively coated onto glass slides. These 2% PSM coatings were tested against aerosol challenges of Gram-negative (Pseudomonas aeruginosa and Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria (107 CFU/mL/30 min). A copolymer soft block containing trifluorethoxy (89 mol %) and C-12 alkylammonium (11 mol %) side chains gave the highest biocidal effectiveness in 30 min: 2 wt %, Gram(+/-) bacteria, 100% kill, and 3.6-4.4 log reduction. A zone of inhibition test showed no biocide release for PSMs and PSM-modified compositions. Characteristics that contribute to concept validation include good hard block/soft block phase separation, a cation/co-repeat group ratio mimicking natural biocidal proteins, a semifluorinated "chaperone" aiding in alkylammonium surface concentration, and a low Tg for the alkylammonium soft block.

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An investigation of the surfaces of linear, segmented block copolymers of poly(dimethylsiloxane−urea−urethanes) by dynamic contact angle analysis is reported. The polymer films are immersed in water, the time-dependent advancing and receding contact angles are observed, and the contact angle hysteresis is reported. The initially hydrophobic polymer surfaces are observed to become more hydrophilic with long-term exposure to water. The advancing contact angles are relatively constant with immersion time; the receding contact angles decrease to some equilibrium value after a few days' exposure to water. It is proposed that the surfaces reorganize by a mechanism in which the hard block urethane−urea domains migrate through the soft block silicone to the polymer−water interface. The surface reorganization kinetics are discussed in terms of the effects of annealing as well as the average molecular weight of the soft block.